1. Technical Field
This invention relates to acoustics, and more particularly, to a system that enhances the perceptual quality of a processed voice.
2. Related Art
Many communication devices acquire, assimilate, and transfer a voice signal. Voice signals pass from one system to another through a communication medium. In some systems, including some systems used in vehicles, the clarity of the voice signal does not depend only on the quality of the communication system or the quality of the communication medium. The clarity of the voice signal may also depend on the amount of noise which accompanies the voice signal. When noise occurs near a source or a receiver, distortion garbles the voice signal, destroys information, and in some instances, masks the voice signal so that it is not recognized by a listener or a voice recognition system.
Noise, which may be annoying, distracting, or result in a loss of information, may come from many sources. Noise from a vehicle may be created by the engine, the road, the tires, or by the movement of air. When a vehicle is in motion on a paved road, a significant amount of the noise it produces may be generated from the contact between the tire and the road—a whooshing or hissing sound one hears as the car passes by. This sound may be particularly noticeable to others driving on the highway with their windows down. The noise may originate from an air pumping effect emanating from the air compression and expansion between the tires of the passing car and the road. This sound may be amplified by the side less horn shape formed by the tire and the road. The short-term, or transient, whooshing or hissing sound as a vehicle passes by a communication device may cause the communication device to suffer voice quality and intelligibility loss, and may also cause speech recognition failure.
Noise estimation techniques may have temporal smoothing parameters to ensure that they do not incorporate speech and temporally short events into their estimates. Because passing tire hiss noise may have a duration similar to that of speech sounds, many conventional noise estimation techniques are unsuitable for identifying passing tire hiss as noise. Instead, passing tire hiss noise may be misinterpreted as signal content and augmented in noise reduction algorithms or misclassified as an utterance in speech recognition applications.
Therefore there is a need for a system that counteracts passing tire hiss noise.